Posted
by
Zonkon Sunday February 12, 2006 @05:28AM
from the it's-in-me-mind! dept.

iiii writes "According to a Yahoo News
story, half of the world's human population is infected with Toxoplasma,
a parasite shown to alter the brain function of rats, inducing them into behavior that benefits the parasite but is suicidal for the rat. So what affect does it have on humans? Article comes complete with Heinlein 'Puppet Masters' reference. I call dibs on using Toxoplasma as a name for my rock band."

Ive read that these parasited are more common in the UK or perhaps we only know of more cases there becuase people are looking harder. Im not exactly an expert on the topic but i know this has been "news" for years now.

perhaps that bactiria [sic] prefers the chemical balance in a bleeding stomach

I believe that h. pylori excretes urease which breaks urea (found naturally in tissues as a byproduct of metabolism) down into ammonia. Ammonia is much more basic than urea, and as a result it reacts with stomach acid to create a more neutral pH, which is better for the organism. Ammonia is also very toxic, which is why the body converts it to urea in the first place (the direct product of metabolism is ammonia, and it is quickly converted to urea to detoxify it before being sent to the kidneys - later it gets partially converted to uric acid which is even less toxic and also requires less water to store/flush (this is what makes bird droppings white - birds do this to the extreme to avoid carrying lots of water in their urine as dead weight when flying)). So, the ammonia is the direct cause of the tissue damage that leads to an ulcer.

The bacteria doesn't really care about blood/pain/holes in stomach - it just wants a break from all that HCl floating around. As long as it nestles in the folds of the tissue it can create a locally moderate environment to grow in.

So, in this case the disease is more a side-effect than a direct goal of the bacteria.

On the other hand, if you look at something like cholera toxin that is something really nasty. Cholera spreads from feces, and its toxin basically makes you run like a faucet (even today it can be quite fatal if not caught early enough - IVs can't fill you up faster than you spill out).

However, you are dead-on that many times disease organisms have the goal of modifying host behavior to encourage spread.

"T. gondii may cause schizophrenia and may do so by producing or triggering the production of an hallucinogenic chemical" ('Genes, Germs, and Schizophrenia: An Evolutionary Perspective', Ledgerwood et al, Perspectives in Biology and Medicine 46(3):317-48, 2003).

But, hey, why keep up with current research (at least via credible objective surveys in reputable journals) when you can just read Wikipedia?

Especially reputable journals whose page title is "Inventions and Ideas from Science Fiction Books and Movies at Technovelgy.com:"

No, I was talking about:

Perspectives in Biology and Medicine

E-ISSN: 1529-8795 Print ISSN: 0031-5982

Publisher: The Johns Hopkins University Press

Perspectives in Biology and Medicine publishes articles of the highest scientific and literary merit on a wide range of biomedical topics such as neurobiology, biomedical ethics and history, genetics and evolution, and ecology. Founded in 1957, this interdisciplinary journal places subjects of current interest in medicine and biology in a context with humanistic, social, and scientific concerns. The editors encourage an informal, humanistic style that preserves the warmth, excitement, and color of the biological and medical sciences.

Human latent toxoplasmosis leads to prolongation of reaction times [11] and changes in personality profiles [12,13]. These changes are probably side effects either of the rodent-aimed manipulative activity of Toxoplasma or of some pathogenic activity of the parasites in the brain. The changes cannot influence the risk of predation in modern humans; nevertheless, prolongation of reaction times could increase the risk of other incidents such as traffic accidents. If this is true then the prevalence of toxoplasmosis in participants in traffic accidents should be higher than in the general population living in the same area.

Here we report the results of retrospective case-control study that compares the seroprevalence of toxoplasmosis in persons injured in traffic accidents with the seroprevalence of toxoplasmosis in general population living in the same area.....

The value of the odds ratio (OR) suggests that subjects with latent toxoplasmosis had a 2.65 (C.I.95= 1.76-4.01) times higher risk of a traffic accident than the toxoplasmosis-negative subjects. "

As it turns out the Times reported on this matter some time ago (unfortunately they have taken down the article...howeverit reported the work of Jaroslav Flegr [natur.cuni.cz] of Charles University Prague...From the report in the times:[Infected] women... appear to exhibit the "sex kitten" effect, becoming less trustworthy, more desirable, fun-loving and possibly more promiscuous.... [They] spent more money on clothes and were consistently rated as more attractive.... By contrast, the infected men appeared to suffer from the "alley cat" effect: becoming less well groomed undesirable loners who were more willing to fight. They were more likely to be suspicious and jealous. "They tended to dislike following rules," Flegr said.Check this [signalplusnoise.com] for more info.

So Toxoplasma triggers the production of LSD in the host organism's brain, and this is believed to be a major cause of schizophrenia in humans? Are there any other sources that support this claim? LSD is somewhat difficult to test for in humans, and even then the link between schizophrenia and LSD is a rather contentious subject in the medical community. The article itself also seems to question the verity of this hypothesis:

"A word of caution: our authors' impressive theoretical edifice is built on some pretty thin evidence. It's simplistic to say T. gondii works by triggering the production of LSD--among other problems with the idea, acid mainly gives rise to visual hallucinations, whereas the delusions of schizophrenics are primarily auditory (e.g., hearing voices)."

As you can probably guess, I am a big fan of acid and psychedelics in general. I've taken many psychedelic drugs, including but not limited to: Cannabis, LSD, Psilocybin Mushrooms, Mescaline, MDMA, AMT, 2C-E, 2C-I, 2C-B, 2C-T-7, 5MeO-AMT, 5MeO-DiPT, Ketamine, DXM, LSA, Salvia, and many others. I've taken traditional psychedelics (Tryptamines and Phenethylamines such as LSD, Psilocybin, Mescaline, MDMA, 2C-*, 5MeO-*, etc.), dissociatives (PCP, DXM, Ketamine, Nitrous, Salvia, etc.), and even deliriants (Dramamine, Datura, Amanita Muscaria, Bella Donna, etc.) on occasion, so I'm pretty well-versed in the various categories of psychedelic drugs and their effects.

Out of the 3 main categories of psychedelic drugs, I would say that the most dangerous is probably the deliriants, typically anticholinergenic deliriants [erowid.org]. Strong dissociatives such as PCP may induce prolonged psychotic states, possibly even causing long-term brain-damage with chronic exposure, but they are unlikely to cause full-blown hallucinations as with anticholinergenic drugs. Conventional psychedelics such as LSD, pot, Mushrooms, Mescaline, etc. are even less likely to induce psychotic/delusional episodes compared to strong dissociatives like PCP. Typically, people on traditional psychedelics such as acid may see OEVs(opened eye visuals) or CEVs(closed eye visuals) but they are not hallucinations in the strict sense. They are more accurately described as perceptual illusions, such as moving patterns, altered spatial perception, synesthesia, etc. Only deleriants cause full-blown hallucinations that one can't distinguish from reality. This is why there is a very high incidence of "bad trips" on deliriants, many of which resulting in ER visits or stays in the psychiatric ward.

While I don't doubt that a bad trip on acid can be the springboard for schizophrenia, these are usually cases where the individual is already predisposed towards mental illness, and the acid simply triggers it by inducing a traumatic experience. Most people, however, walk away from their bad trips relatively unscathed. Some naive users may continue to be haunted afterwards by embarassing things they did while they were tripping, but few suffer any long-term psychological effects from their bad trips.

I have simply known too many people who have done acid or similar hallucinogens and have never exhibited any psychotic behavior to believe that LSD can cause schizophrenia. In fact, I don't think that LSD plays much of a role in the etiology of schizophrenia or any other mental illness. It's more likely that most people who develop schizophrenia after taking LSD would have still developed the mental disorder eventually even if they hadn't taken any drugs.

I've only met 3 individuals whom I've witnessed really bizarre behavior from after they took psychedelic drugs. One appeared to experience acute psychotic episodes after smoking pot or drinking alcohol, but this seemed to be due to his being socially maladjusted more than anything. The second individual behaved very strangely after consuming mushrooms on 2 different occassions, but otherwise he was perfectly normal even when he smoked weed or

Toxoplasma gondii is a protozoan which has cats as its definitive host. It has a wide range of intermediate hosts, and is capable of infecting all warm-blooded vertebrates, including humans. Toxoplasma lives inside the epithelial cells lining the intestine of its feline host. Eggs are shed with the faeces, and can survive in soil for several months. Toxoplasma cells can also penetrate work their way out of the intestine and infect almost any other cell type, eventually forming cysts in the host's brain, liver and muscles. Intermediate hosts are infected either by eating food or water contaminated with infected cat faeces; by eating undercooked meat from other intermediate hosts containing Toxoplasma cysts; or, in the case of some unfortunates, via the placenta from an infected mother.

Back to the rats. Rats are easily infected with Toxoplasma, and have been the subject of a lot of experimentation. Infection tends to lead to the establishment of Toxoplasma cysts in the brain, and alteration of the rat's behaviour. Infected rats tend to be more active and less afraid of novelty, both of which behaviours are likely to place the rat at increased risk of predation by cats. The changes go further than that, however. Rats are inherently, and understandably, afraid of the odour of cats. Even lab rats which have not been exposed to cats for generations will avoid areas marked with cat urine. Toxoplasma infected rats do not, however, share this aversion; in fact, rats tested in pens marked with different types of scent (rat urine, cat urine, rabbit urine and water) actually seemed to be suicidally attracted to the cat-scented areas . The infected rats appeared to be completely healthy in all other ways.

The implications of this research are enough to send a frisson of fear down the spine of anyone, devoted parasitologist or otherwise. Toxoplasma infection is common amongst humans. It has been estimated that 30% of the global human population may be infected, with prevalence in specific countries ranging from 22% in the UK to 84% in France. Can the parasite affect human behaviour in the way in which it affects that of rats? The answer appears to be "yes".
One manner in which this happens is via direct damage to the host's brain and central nervous system. Babies born to mothers infected with Toxoplasma early in fetal development can suffer from widespread disease, including mental retardation . Infection later in development can lead to a persistant infection with no apparent symptoms, with the parasite forming cysts in the brain. With any luck the immune system can keep the parasite under control; depression of the immune system, however, can result in its reactivation, with consequent neurological or psychiatric effects.

It has also been suggested that prenatal exposure to toxoplasmosis can increase an individual's susceptibility to schizophrenia , but because of the difficulty of experimenting in this area, there is little supporting evidence , although it is interesting to note that several of the drugs used in the treatment of schizophrenia and bipolar disorder inhibit the replication of Toxoplasma .
Does the manipulation hypothesis hold in humans? If it does, it must be only as a non-adaptive side effect of the ability to manipuate hosts such as mice and rats, since, as Joanne Webster points out in a fascinating review article on the subject , humans are rarely preyed upon by cats. There does appear to be some evidence that human personality traits are affected by Toxoplasma infection, but the one study that has specifically looked for an effect is less than wholly convincing. Flegr and Hrdý, found that men with chronic Toxoplasma infections had a greater tendency to disregard rules and were more suspecting, jealous and dogmatic than non-infected controls . However, the number of males tested was only 195, of whom 56 were infected, and the effect disappeared entirely if the male and female subjects were analyzed together. This research provides a fascinating, if somewhat disturbing, hint of an effect, but it seems safe to say that most of us are more than mere parasite-controlled robots.

But toxoplasmosa gondii is able to hide from the immune system, usually in cysts in the muscles or the brain. So the number of people with antibodies to it is roughly the number of people who have it hidden away in their bodies.

Apparently toxoplasmosa is only a danger for pregnant women if they get their *first* ever infection while pregnant, during the last trimester.

And you can get it from unwashed veggies and undercooked meat (see the first paragraph about toxoplasmosa hiding away in muscle).

This connects well with the known etiology of toxoplasmosis, and is why the MD tells your pregnant wife/girlfriend/mom to stay away from cats.

Specifically, cat poop. Sorry, it may sound like nit-picking to you, but you should see the number of cats who wind up in shelters because their owner got pregnant. Pregnant women do NOT need to stay away from cats - they just need to stay away from the litter box. They shouldn't clean it, and should avoid inhaling dust from it. If your cat has something wrong with it and can't clean its bum properly, someone (who's not pregnant) should be keeping it clean for them. Only single pregnant women with no one to take care of this stuff for them might need to actually rehome their cats - and they can usually wear gloves and a surgical mask when cleaning the litterbox.

Actually, there is another hypothesized threat from Toxoplasma gondii that is a deadly risk even for people with just a dormant infection. (Toxoplamsa doesn't get eliminated by the immune system; it just goes dormant in cysts in the muscle tissue and brain and continues to effect its host for life.)

There are numerous studies which indicate that latest T. gondii cyst infection produces a noticeable drop in motor skills and intelligence. I wrote an article [kuro5hin.org] on this over at K5 a couple weeks ago. One of the comments [kuro5hin.org] linked to a study [biomedcentral.com] which showed a significant increase in risk of traffic accidents for those with latent T. gondii infection.

However, the notion that this is a "mind control" parasite in humans is completely off base. A previous study showed that mice infected with T. gondii had increased risk of cat predation. Researchers believe that may be caused by increased dopamine levels in mouse brains as a result. But that is still speculative.

I could add that I submitted this story to/. almost three weeks ago and was rejected within an hour... but that would be off topic.

I get your point, and love my cat, too, but the precautions need to be a bit more than you make out. Cats who "clean up" themselves by licking the fur around their rectum just push the infectious material around their fur. After the saliva dries, T. gondii remains infectious for some time afterwards. Really, pregnant women should wash their hands after handling cats.

That said, nobody should "re-home" an animal just because they're too lazy to take a little extra effort for 9 months, unless you're talking about "re-home" as in "here mom, take care of my cat for a few months and I'll take her back".

I do understand that the chance of becoming infected is low. It's important too to acknowledge that the damage of infection is catastrophic. (Pun fully intended)

If you actually read the whole article, you would've seen this sentence: "In fact, antipsychotic drugs were as effective as pyrimethamine, a drug that specifically eliminates Toxoplasma." (emphasis mine)

You are right. I'm from Argentina, and we were taught about Toxoplasmosis in 6th grade biology class (that's when we were 11 years old).

It usually is not dangerous, and the body gets rid of it quite easily (it takes a month or so, with flu-like symptoms), the biggest problem with it is getting the infection during a pregnancy, which can cause malformations in the fetus.

Typically you catch it from contact with cats (thats why woman who hadn't had toxoplasmosis shouldn't be in contact with cats during the pregnancy).

I'll probably burn some karma with this, but what caught my attention is that I assumed that the knowledge about it would be vox-populi, since it was taught to me in primary school.

If my wife is pregnant, and there's a fraction of a percent chance that my cat could cause serious complications for her or the baby, guess what... the cat dies. Well, not really. But the cat is certainly gone.

While I can certainly agree with your point about priorities, this strikes me as nonsensical. Just about every activity in life carries with it risks. Statistically speaking, your hypothetical pregnant wife has many times more of a chance of losing her baby (and her life) by driving a car than by handling cat feces. But how many pregnant women avoid driving a car? Given the impracticality, I wouldn't think many.

This is really all about cost and benefit. As good as it may sound to say, you would not eliminate EVERYTHING in your life that causes your unborn baby even the slightest risk of death. Besides being impractical in many cases, it would just make you miserable for no measurable payoff. You may take precautions that can reduce the risk for many of the risks and that is normal for most parents to be.

Back to cats: assuming you own a cat, you bought the critter for a reason. It brings something to your life and that is the reason you got it. Now entirely eliminating that benefit for a tiny chance of infection (a percentage which is dwarfed by many, many other risks you probably take daily) just doesn't seem very rational to me. If the chance of infection via the cat were greater (IOW, higher than insignificant), or there were no reasonable precautions you could take against infection, then I could understand it.

Like most other issues, this gets blown out of proportion by reactionaries, especially in the media. The risk is small, but talking to some people, it would seem as though every cat in the world should be killed.

So get the facts before you go out making a bad decision. Some spend years training, getting to know and form a bond with a cat just to piss it away because of an irrational fear. That is just poor decision making, in my book.